Many people suffer from disabilities that affect their life activities. Fortunately, some disabilities can be ameliorated or even alleviated through the use of engineered devices. For example, a cane or walker can help someone with strength or balance problems, while a pacemaker can improve a cardiac patient's quality of life.
One common assistive device that is beneficial to both temporarily- and permanently-disabled individuals is the wheelchair. These are available in a wide range of styles, from light-duty, temporary chairs, to racing and cross-country chairs and fully-powered electric models. Although wheelchairs can be useful in a variety of situations, lower-body and leg injuries are disproportionately common among the difficulties faced by a wheelchair user.
For this reason, many chairs include leg-support structures (generically, “leg rests”) to improve user comfort and convenience. Of course, users' bodies are different sizes and proportions, so it is important for the leg rests (as well as other parts of the chair) to be adjustable, and to be carefully adjusted to fit the user. With respect to leg rests in particular, a problem often encountered is that the rests must be moved, raised and lowered (e.g., to provide suitable ground clearance), and rotated (or swung) up and down (extending the leg) to improve comfort or promote circulation.
A number of mechanisms for adjustable and extensible leg rests are known in the art, but a common problem is that the effective rotation center of many rests is offset from the leg-rotation (extension) center at the user's knee, which causes either the flexed or extended leg-rest length to be wrong. (In other words, a leg rest properly adjusted for length in the flexed position, is too short in the extended position; or vice versa.) Mechanisms designed to address this problem are often complex, heavy or prone to breakage. Furthermore, such existing mechanisms are incompatible with standardized, mass-produced, inexpensive leg-rest components that fit many existing wheelchairs. (FIG. 2 shows an example “universal” leg rest 210, including the standardized attachment points 220 and 230, which mate with corresponding points 240 and 250 of compatible wheelchairs This Figure also shows the length adjustment feature of the leg rest 260 and a fold-down foot rest 270.)
A new wheelchair accessory that can convert a standard wheelchair and universal leg rest into a length-corrected, extendable leg rest may be of significant value to many wheelchair users.